1. Field of the Invention
The prevent invention relates to a lead frame conveying apparatus for use in the manufacture of, for example, a semiconductor device.
2. Description of the Related Art
FIGS. 15 and 16 show a conventional lead frame conveying apparatus. In FIGS. 15 and 16, a shaft 2 is rotatably mounted on one-end sides of guides 6-1 and 6-2 and driven by a motor 1 mounted on the guide 6-1. Rollers 3-1 and 3-2 are provided on the shaft 2 such that they are spaced apart at a predetermined interval. A shaft is mounted on the other-end side, not shown, of guides 6-1 and 6-2. Two rollers, not shown, are provided on the shaft, one roller being paired with the roller 3-1 and the other roller being paired with the roller 3-2. A belt 4-1 is wrapped between the roller 3-1 and the corresponding paired roller and a belt 4-2 is wrapped between the roller 3-2 and the corresponding paired roller. The belts 4-1 and 4-2 are rotated by being driven by the motor 1. A lead frame 5 is placed on the belts 4-1 and 4-2 and conveyed with the rotation of these belts 4-1 and 4-2.
In the arrangement thus explained, the lead frame 5 is contacted with the belts 4-1 and 4-2 only at those areas near its opposite sides extending in a direction of conveyance of the lead frame with a middle portion of the lead frame 5 not contacted with the belts 4-1 and 4-2. This is because a bed, on which an IC chip, etc., is placed, as well as inner leads for supplying an electric power and signal to the IC chip, are placed at the middle portion of the lead frame 5, that is, because, being contacted with the belt, the bed and inner leads cannot maintain their clean level.
The guides 6-1 and 6-2 prevent the lead frame 5 from being dropped during conveyance of the lead frame. The guides 6-1 and 6-2 have nuts 7 with their threaded directions reversed with respect to each other. The nuts 7 are threadedly mounted on a screw shaft 8. The screw shaft 8 has threaded portions whose directions are reversed with the middle of the shaft 8 as a boundary. The screw shaft 8 is driven by a motor 9. With the rotation of the screw shaft 8, the guides 6-1 and 6-2 are moved in the mutually opposite directions. The distance between the guides 6-1 and 6-2 can be adjusted by varying the rotation direction of the screw shaft 8. For this reason, various kinds of lead frames of different sizes are conveyed on a single conveying apparatus.
It is, therefore, necessary to adjust the distance between the guides 6-1 and 6-2 each time a different kind of lead frame is conveyed on a conventional apparatus. It takes up a lot of time and effort.
Further, more component parts, including the nuts 7, screw shaft 8 and motor 9, are necessary to move the guides 6-1 and 6-2. Thus the apparatus becomes complex in construction and expensive. More component parts require more labor in the repair and checkup of the apparatus and are liable to fail, thus posing a reliability problem.